The present invention relates generally to shifting mechanisms and more particularly to an improved control mechanism wherein a single lever can be utilized for controlling two different movable control elements.
With the increased automation of various operations, particularly in the field of agricultural equipment, most present day tractors incorporate a number of controls that must be individually controlled by the operator. For example, multi-speed, multi-range transmissions have been incorporated into large agricultural tractors in recent years. One example of such a transmission is disclosed in Bislew U.S. Pat. No. 3,469,472. The transmission disclosed therein consists of two different units that are operatively interconnected so that the vehicle can be operated in as many as twelve different speeds in the forward direction and four speeds in the reverse direction. The transmission disclosed in the Bislew patent incorporates a multi-speed planetary drive unit which is coupled to a multi-speed sliding gear unit so that the planetary gear unit can be set for three forward speeds and one reverse speed. The multiple speed sliding gear unit is designed so that the vehicle can be operated at four different ranges for any one of the four different settings for the planetary unit. Thus, the operator has the capability of operating the vehicle at twelve different forward speeds and four different reverse speeds.
One of the problems encountered with multi-speed transmissions of this type is that such a unit requires a large number of control elements. For example, the transmission shown in the Bislew patent requires actuation of two control elements for the sliding gear unit and a further control element for operating the main control valve that shifts the planetary drive unit as well as a foot pedal for operating the modulating valve.
It has now been proposed to further increase the versatility of the transmission of the type disclosed in the Bislew patent to double the number of speeds at which the unit can be operated. This can be accomplished by producing an input into the transmission which is operated at two different speeds. This can be performed by a clutch arrangement between the engine and the input shaft for the transmission disclosed in the Bislew patent. However, the arrangement requires a further control valve for actuating the clutch. The additional clutch of necessity requires a further or fourth control element for actuating the control valve that cooperates with the input clutch.